Carburetor



C. L.. MARTIN Feb. 14, 1967 CARBURETOR Filed May 22, 1964 I N VEN TOR.

YAGENT United States Patent 3,304,047 CARBURETOR Charles L. Martin, St. Louis, Mo., assigner to ACF Industries Incorporated, New York, N.Y., a corporation of New Jersey Filed May 22, 1964, Ser. No. 369,369 5 Claims. (Cl. 251-118) This invention relates to carburetors for internal combustion engines, and particularly to float actuated needle valves for maintaining a predetermined constant fuel level Within a fuel bowl.

Foal actuated needle valves for carburetors have historically comprised a valve body having a metallic seat for engagement by the tapered end of a metallic needle to control the ow of fuel into the fuel bowl. Recently valve needles having elastomeric sealing tips have been introduced for seating against a metallic seat to cont-rol the flow of fuel into the fuel bowl as disclosed in Patent No. 3,086,750 to Carlson et al. Elastomeric materials have also been employed as seat members in carburetors and are engaged by a metallic needle to control the flow of fuel. To prevent leakage and flooding of the carburetor, the needle and seat must be manufactured to exact tolerances, and the fuel must be free from particles of foreign material which might interfere with proper seating of the needle. Regardless of the type of valve needles or the type of valve seats which are utilized to control the ow of fuel, the flow path followed by Ithe fuel, as it flows past the valve seat and the valve needle and through the valve body into the oat chamber of the carburetor, is generally tortuous and turbulence is induced into the fuel ow at several points along the ow path. Turbulence in the flow of fuel causes back pressure to be induced which opposes the ow and thereby restricts the amount of fuel which will ow through the valve. Where needle seat structures are employed utilizing ared elastomer tipped needles, the flare formed immediately below the tip induces a severe turbulent condition in the fuel flow, which causes back pressure directly against the lower surface of the needle flare, thus inducing a fo-rce which opposes the direction of free needle travel and which limits the amount of needle travel away from the seat. Restricted valve movement limits the effective size of the valve seat opening and also limits the amount of fuel which :will ilow through the valve. Excessive turbulence also causes the valve needle to vibrate or to oscillate during high fuel ilow so that the flow of fuel may become erratic and the engine may be starved during high speed maximum full demand periods.

Since larger and more powerful automotive engines are being developed, which utilize larger portions of the available engine compartment space of the automobile, a need has developed for accessories such as fuel pumps, carburetors, and the like, to be more `compact in design so that more space is available for the engine and all of the many accessories which are powered by the engine. Since more powerful automobile engines generally require a greater quantity of fuel than lchat required by smaller engines, a need has developed for carburetor design for l larger engines to incorporate a reduction in overall dimension and yet an inc-rease in the amount of fuel ilow capacity, as compared to present carburetors. In order to effect an increase in the flow of fuel into the fuel bowl of a carburetor without increasing the overall dimension of lthe carburetor to satisfy lthe increased fuel demands of these more powerful automobile engines, it was assumed that merely enlarging the needle valve seat and providing a larger conical surface on the needle would provide suicient fuel flow. It was discovered, however, that an increase inthe diameter of the cylindrical end portion of the needle would require an increase in the diameter of the Patented Feb. 14, 1967 ICC triangular stock, from which the needle is formed,`thereby resulting in a needle of increased size and weight and increasing the cost of the needle by such an amount that such an increase would be impractical. It was further discovered that an increase in the size of the triangular stock Would result in a decrease in the size of the flow passages dened between the needle and the bore in which the needle reciprocates, thereby restricting the volume of fuel flow. The bore in which the needle reciprocates, therefore, must be enlarged to allow suflicient fuel flow past the enlarged needle valve. An increase in the size of the bore in which the needle reciprocates would not only require an increase in the size of the triangular needle stock ibut would also require lengthening of the bearing surfaces of the needle to control the alignment between the needle and the seat. Lengthening of the needle yand seat would result in a need for moving the pivot point of the float and for increasing the length ofthe float arm to establish an optimum engagement between the oat arm and the needle vlave. It is, therefore, seen that merely changing t-he diameter of the cylindrical portion `of the needle valve would result in a series of necessary design changes which would increase the overall size and cost of the carburetor, thereby rendering such changes impractical.

It is, therefore, an object of this invention to provide a novel carburetor needle valve structure which requires a minimum -of space and which is adapted to provide a maximum of fuel flow through a given size orifice.

Another obje-ct of the invention resides in the provision of a novel carburetor needle valve which promotes a smooth ilow of fuel during pressure reduction of the fuel as the fuel leaves the fuel inlet recess and passes through the valve seat.

A further object of this invention resides in the provision of a novel carburetor needle valve body having side openings therein which are larger than the dimension of the orice and yet which maintain optimum needle guide surface.

An even further object of this invention contemplates the provision of a novel carburetor needle seat wherein the surface tension forces between the needle and the seat are effectively reduced.

Another object of this invention resides in the provision of a novel carburetor needle valve structure which is adapted for eflicient and smooth needle movement and thereby allowing a maximum of fuel flow kat all ow conditions.

Other and further objects of this invention will be obvious upon an understanding of the illustrative embodiment about to be described, or will be indicated in the appended claims, and various advantages not referred to herein will occur to one skilled -in the art upon employment of the invention in practice.

A preferred embodiment of the invention has been chosen for purposes yof illustration and description and is shown in the accompanying drawings, forming a part of the specification, wherein;

FIGURE 1 is a side elevation in several partial sections, illustrating a carburetor provide-d with a oat actuated needle valve, embodying features of the invention.

FIGURE 2 is an enlarged :fragmentary longitudinal section illustrating the needle valve structure of FIG- URE 1.

FIGURE 3 is a transverse plan view of the needle structure of FIGURE 2, taken along lines 3 3 of FIGURE 2.

Briefly, the invention comprises a carburetor needle valve assembly generally comprised of a valve lbody formed with a fuel passage and a valve needle mounted for lreciprocation within the fuel passage to control the flow of fuel into the fuel bowl of the carburetor. The valve body lstructure is so formed that the Ailow of fuel through the needle valve str-ucture is accomplished with a minimum of turbulence, thereby achieving a maximum rate of fuel flow through a `given size valve orifice.

Referring now to the drawing for a better understanding of the invention, a down-draft carburetor is shown in FIGURE 1 as comprising an air horn :section 2, a mam body section 3 and a throttle outlet section l4.- Said sections being secured together and forming a mixture conduit 6, having a stack of venturies 7, 7a and 7b in the main Abody section. The :carburetor is mounted `on the intake manifold M of a conventional internal combustion engine N, adapted for use in driving a vehicle.

A choke valve 9, operable responsive to intake air ow, is rotatably mounted in an unbalanced manner on a valve shaft 10 in the air horn section 2, which forms the air inlet end of the mixture conduit 6. A throttle valve 8 is rotatably mounted on a shaft in the outlet end of the mixture conduit 6.

The main carburetor body section 3 is provided with a fuel lbowl 12 having a fuel inlet 13 provided with a screen lter 14, xed within an inlet recess 13a. A fuel inlet valve 16, includes a needle valve having a tapered point 34 in contact with a valve seat of a valve body structure 16 to control fuel ow from the inlet 13 into the fuel lbowl 12. A float 17 carries an arm 17a pivotally mounted at 18 within the :f-uel bowl to actuate the needle valve 30 for maintaining a substantially constant fuel level within the bowl 12. Fuel is supplied to the bowl from a fuel tank -by means of a conventional engine operated fue] pump 20 interposed in a fuel conduit 25 leading to the fuel inlet 13.

A fuel metering orifice 19 leads from the fuel 4bowl 12 to an upwardly inclined main fuel passage 21, having a main fuel nozzle 22, discharging into the primary venturi 7. Fuel flow from bowl 12 through the orifice 19 and into the fuel passage 21 is controlled by a metering rod 40, having a stepped end 41 positioned in the metering orice 19. Movement of the rod to lposition a different stepped portion in the orifice 19 provides a change in fuel flow through the orice 19. An idle fuel system is shown as comprising a fuel well 23, leading upwardly `from the main fuel passage 21. The well 23 has a metering tube 24 therein, communicating with the idle passa-ge 26 provided by idle ports 27 and 28. The well 23 has a metering tube 24 therein, communicating with an idle passage 26, provided with the idle ports 27 and 28. An idle adjustment screw 29 is provided for the idle port 28.

Therf'uel inlet valve 16 includes a valve needle 30 formed with a body 32 of noncircular cross section, as illustrated in detail in FIGURES 2 and 3. One end of the needle 30 is formed with a conical tip 34 and the other end of the needle 30 is formed with a rounded head 40, for engagement by a float arm 17a, as illustrated in FIG- URE l. The needle V30 is formed with a plurality 4of ribs 31, each having a partial cylindrical surface 33 formed thereon which is in guiding engagement with a cylindrical bore 42 lformed in the valve body 16, whereby the needle 30 is positioned for free reciprocal movement within the :cylindrical bore 42. The upper end of the valve body 16 is forme-d with external threads 44, FIGURE 1, for detachable engagement within a threaded aperture leading through a Wall of the carburetor to the inlet recess 13a.

The valve lbody 1-6 is formed with a second cylindrical bore 46 coaxially aligned with the bore `42 and of smaller diameter. As illustrated in FIGURES 2 and 3, an annulai seat ring 36 formed of elastomer material is held against a shoulder 37 formed by the Ibore 42 by a retainer ring 39 and defines a valve seat 38 for the tip 34 of the needle 30.

The tip 34 of the needle valve 30 may Ibe formed by turning a generally conical surface on one end of the needle 30, yas illustrated in FIGURES 2 and 3, or the conical tip 34 of the needle valve maybe formed of a synthetic rubber material which is not effected by contact with fuel. Reference may be had to Patent No. 3,086,750 to Carlson et al. :for the teaching .of providing a needle with an elastomer tip. The specific valve needle and valve seat structure set forth -a-bove is, therefore, merely illustrative and must not `be taken in a limiting sense. Various needle and seat `structures may be incorporated into this invention without departing lfrom the spirit or the scope thereof.

In operation, fuel is forced by pump 20 from the fuel source or fuel tank 15 through fuel connection-s 25 into the inlet 13 of the carburetor. Fluel will flow through the screening 14 and the fuel passages 46 and 52 past the needle valve 30 when the iioat structure 17 of the carburetor is in a downward position to lrelease the needle 30 from its fuel passage closing position. When the fuel bowl 12 is filled to the desired predetermined level, a float lever 17a will force the needle valve 30 against the valve seat 38 and close olf `.further fuel to the carburetor. During engine operation, fuel fills the fuel passa-ge 21 to the same level -as within the bowl. Air flow through the mixture conduit 46 passes through the venturi stack 7-7a, causing a low pressure area at the mouth of the fuel nozzle 22. Atmospheric pressure on the fuel level in the fuel bowl forces fuel lup to the fuel passage 21 and :out of the nozzle 22 to mix with the air in the mixture conduit 6. The ow of air and fuel mixture into the manifold M of the engine is controlled in a well-known manner by the manually operated throttle valve 8.

As the fuel flows from the fuel bowl 12 through the fuel passage 21 and the fuel nozzle 22, the level of fuel in the bowl 12 is lowered, with a resulting lowering of the position of the float 17. The downward movement of float arm 17a in response to lowering of the float 17 permits the fuel valve 30 to drop downwardly under the combined forces of gravity and fuel pressure to permit the flow of fuel from the inlet 13 into the fuel bowl 12 to replenish the fuel consumed by the engine.

In accordance with the invention, as illustrated in detail in FIGURES 2, 3 and 4, opposing portions of the wall structure of `the valve body 16 are cut away, such as by milling or the like, to define opposed openings 52 and 54, the combined area of which is greater than the area delined by the valve seat 38. A pair of opposing substantially planar surfaces S6 and 58 are formed on the valve body 16 and are disposed' transverse to the axis of the valve body 16. The planar surfaces 54 and 56 are inclined with respect to an axis of the bore 42 to substantially the same degree as is the conical surface 34. For example, if the conical surface 34 is formed with a 60 angle relative to the axis of the bore 42, the surfaces 56 and 58 will also be inclined substantially 60 relative to the axis of the bore 42.

A pair of opposed substantially planar surfaces 57 and 59 are formed in the valve body 16 below the valve seat 38 and are disposed substantially normal to the axis of the 'bore 42. The pairs of planar surfaces 56-57 and 58-59 cooperate to define a pair of opposed outwardly diverging passages for conducting the fuel from the openings 52 and 54 into the fuel bowl 12.

Forming the outwardly diverging passages in the Wall structure of the valve body 16, achieves a number of results which effectively provide improved fuel flow. The turbulent condition which is generally found immediately below the valve seat 38 in most needle valve structures is effectively reduced thereby allowing a smoother flow of fuel past the valve seat and into the fuel bowl. This turbulent condition is caused by a reduction in the fuel pressure which causes violent agitation of the fuel. As fuel under pressure developed by the fuel pump 20 flows through the bore 46 past the valve seat 38, the pressure of the fuel is suddenly reduced from approximately nine: pounds per square inch above atmospheric pressure to atmospheric pressure. Since volatile fuel which as gasoline is normally utilized in automotive engines, the fuel owing past the valve seat 38 will tend to vaporize as its pressure is reduced to atmospheric pressure causing the formation of vapor bubbles. The vapor bubbles tend to expand the volume of the fuel and cause violent agitation of the fuel immediately below the valve seat. This agitation adds to the natural tendency for the flow of uid past the valve seat to swirl or eddy and to produce a back pressure opposing the flow of fuel. As illustrated in FIGURES 2 and 3 the outwardly diverging surfaces forming the openings 52 and 54 allow the vapor bubbles immediately below the valve seat 38 to quickly dissipate -outwardly into the fuel bowl 12. This prevents the development of excessive back pressure which would otherwise tend to oppose the flow of fuel and allows a smooth flow of fuel past the valve seat and into the fuel bowl. As the fuel ows past the Valve seat 38 it is directed by the conical surface of the tip 34 and by the outwardly diverging surfaces 56 and 58, as illustrated in FIGUR-E 3, to flow smoothly into the fuel bowl 12.

The invention effectively prevents excessive restriction of needle valve movement by the vapor -bubbles which form in Vthe fuel at the instant of pressure reduction. In rnost needle valve structures currently being manufactured, the vapor bubbles which form immediately below the valve seat within the valve body must ow with the fuel along the needle body to the outlet at the free eX- tremity of the valve seat. Surface tension developed between the vapor 'bubbles and the needle valve walls and valve body walls tends not only to restrict the flow of fuel in the How channels of the valve but also to restrict the amount of needle travel from the valve seat, which adversely affects the flow of fuel through the valve. As illustrated in FIGURE 4, a plurality of fuel ow channels 60 defined between the body 32 of the needle 30 and the bore 42 serve to conduct the flow of fuel through the valve body 16. The vapor bubbles, which form immediately below the valve seat 38 (FIGURES 2 and 3) along with the turbulent fuel will dissipate quickly outwardly into the fuel bowl 12. The remaining fuel which flows through the channels 60 (FIGURE 4) and into the fuel bowl 12 at the free extremity of the valve body 16 will be smooth, constant and substantially bubble-free. The substantially bubble-free ow of fuel through channels 60 of the valve will allow maximum needle movement without the back pressure or restriction caused by the bubble laden uid.

Back pressure which would otherwise tend to restrict fuel flow is effectively relieved through the opposed openings 52 and S4. The combined cross sectional dimension of the openings 52 and 54, being greater than the cross sectional dimension of the valve seat 38, effectively prevent the formation of excessive back presure which would oppose fuel flow through the valve seat 38. The opposed outwardly diverging passages formed by the op-posed surfaces 56-57 and 58-59 tend to allow further pressure reduction during the flow of fuel thereby preventing any tendency to retard the flow of fuel.

The novel construction of this invention also involves a minimum of direction change in the flow of fluid which also aids in the prevention of excessive back pressure and' turbulence and thereby further aiding the flow of fuel. As the fuel flows past the conical tip 34 ofthe valve needle, the fuel will flow along the surfaces 56 and 58 thereby involving very little flow direction change and promoting more efficient fuel flow.

From the foregoing, it is seen that I have produced a novel needle valve structure for a carburetor which is of a minimum overall dimension and yet which is capa-ble of a much greater flow of fuel than has been obtained heretofore. The invention also promotes a smooth ow of substantially bubble-free fuel through the flow channels between the valve needle body and the valve body bore thereby preventing excessive back pressure which would tend to restrict fuel ow and needle movement. The invention effectively provides for quick dissipation of vapor bubbles which are formed during reduction of the fuel pressure and eliminates excessive back pressure and tur- Ibulence in the valve body which would otherwise restrict fuel flow and needle travel. The flow of fuel through the valve is subjected to a minimum of direction change which effectively promotes smooth and rapid fuel llo-w while inducing a minimum of turbulence in the fuel. The invention, therefore, is one well adapted to attain all of the objects hereinabove set forth, together with other advantages which are obvious and inherent from the description of the apparatus itself.

It will be understood that certain features and subcom- =binations are of utility and may be employed without reference to other features and subcombinations. This is contemplated by and is within the sco-pe of the claims.

As many possible embodiments may be made of the invention without departing from the scope thereof, it is to be understood that all matter herein set forth or shown in the accompanying `drawings is to be interpreted as illustrative and not in a limiting sense.

I claim:

1. A carburetor f-or an internal combustion engine having a fuel inlet, a valve structure for controlling the ow of fuel through the inlet, said valve structure including a valve body having a fuel passage therethrough connected to the fuel inlet and an annular valve seat formed within the fuel passage, Aa valve needle mounted for longitudinal movement within the fuel passage, a conical tip on one end of the valve needle adapted to engage the valve seat to block the flow of fluid through the valve, at least one pair of outwardly diverging substantially plana-r surfaces formed intermediate the length of the valve body and defining at least one outwardly diverging passage which communicates with the fuel passage through an opening having a greater area than the area dened by the annular valve seat.

2. A carburetor for an intern-al combustion engine having a fuel inlet, a valve structure for controlling `the flow of fuel through the inlet, said valve structure including a valve body having a fuel passage therethrough connected to the fuel inlet and an annular valve seat formed within said fuel passage, a valve needle mounted for 1onlgitudinal movement within the fuel passage, a conical tip on one end of the valve needle adapted to engage the valve seat to block the flow of fuel through the valve, opposing pairs of outwardly diverging substantially planar surfaces formed intermediate the length of land in transverse relation to the valve body and defining a pair of opposed outwardly divenging passages which communicate with the fuel passage through openings having a combined area Igreater than the area defined by the annular valve seat.

3. A carburetor for an internal combustion engine having a fuel inlet, la valve structure for controlling the ow of fuel through the inlet, said valve structure including a valve .body having a fuel passage therethrough connected to the fuel inlet and an annular valve seat Iformed within said fuel passage, a valve needle mounted for longitudinal movement within the Ifuel passage, -a conical tip on one end of the valve needle adapted to engage the valve seat to block the flow of fuel through the valve, opposing pairs of outwardly diverging substantially planar surfaces formed intermediate the length lof the valve body Iand defining a pair of 'opposed outwardly -diverging passages which communicate with the fuel passage through an opening having a greater tarea than the area defined by the annular valve seat, one -of the planar surfaces o-f each of said pairs of outwardly diverging surfaces being disposed substantially norm-al to the fuel passa-ge and the other surface of each of said pairs being of substantially the same angul-ar relation with the fuel passage as the angular relation between the conical tip and the fuel passage.

4. A needle valve assembly adapted to be `mounted within the fuel inlet passage of a carburetor having a fuel bowl, said assembly comprising; a -valve body having a flow passage formed therethrough `for communicating said inlet passage with said fuel bowl, means dening Aa valve seat within s-aid flow passage, a valve needle having a conical surface -fonmed on one extremity thereof being positioned within the flow passage and movable from a closed position, where the conical surf-ace engages the valve seat to prevent the iiow of `fuel through the `flow passage, to an yopen position where the conical surface is spaced from the valve seat to all-ow fuel to flow through the flow passage, means for imparting movement t-o said valve needle, at least one outwardly diverging passa-ge formed in the valve body intermediate the length thereof and communicating the flow ipassage with the lfuel bowl, said outwardly diver-ging passage being defined by :a rst substantially planar surface -disposed substantially normal to the iiow passage and a second substantially planar su-rface ydisposed in substantially the same angular relation with the ow passage las the angular relation between the conical surface of the valve needle and the ow passage, Whereby, upon cooperation of the conical surface and the second surface, =a smooth iiow of fuel will be induced through the needle valve assembly yand into the fuel bowl.

5. A needle valve 'assembly `for Ia carburetor having a fuel bowl, said assembly comprising a valve body having a fiow passage and -a valve seat intermediate the length of the iiow passage, a valve needle having a conical surface formed at one extremity thereof disposed within the flow passage and being movable between open and closed positions relative to the How pass-age to control the ow of fuel int-o the yfuel bowl, at least one pair of outwardly diveriging substantially planar surfaces lformed in the valve body and disposed transverse to the ow passage, one of said planar surfaces vbeing disposed substantially normal to the flow passage and the other of said planar surfaces having substantially the same angular relation with the flow passage as the angular relation |between the conical surface of the valve needle Iand the flow passa-ge, said surfaces Idefining lat least one outwardly diverging passage for communicating the ilow passage land the fuel bowl, the outwardly diverging passage cooperating with the conical surface of the valve needle to lprevent excessive turbulence in the flow of fluid into the fuel bowl.

References Cited by the Examiner UNITED STATES PATENTS 2,172,935 9/1939 Ewart 251-118 3,054,594 9/19162 Hecht 137-434 X 3,059,898 10/1962 Carlson et al 137434 X FOREIGN PATENTS 452,106 8/ 1936 Great Britain. 732,071 `6/ 1955 Great Britain.

M. CARY NELSON, Primary Examiner.

R. C. MILLER, Assistant Examiner. 

1. A CARBURETOR FOR AN INTERNAL COMBUSTION ENGINE HAVING A FUEL INLET, A VALVE STRUCTURE FOR CONTROLLING THE FLOW OF FUEL THROUGH THE INLET, SAID VALVE STRUCTURE INCLUDING A VALVE BODY HAVING A FUEL PASSAGE THERETHROUGH CONNECTED TO THE FUEL INLET AND AN ANNULAR VALVE SEAT FORMED WITHIN THE FUEL PASSAGE, A VALVE NEEDLE MOUNTED FOR LONGITUDINAL MOVEMENT WITHIN THE FUEL PASSAGE, A CONICAL TIP ON ONE END OF THE VALVE NEEDLE ADAPTED TO ENGAGE THE VALVE SEAT TO BLOCK THE FLOW OF FLUID THROUGH THE VALVE, AT LEAST ONE PAIR OF OUTWARDLY DIVERGING SUBSTANTIALLY PLANAR SURFACES FORMED INTERMEDIATE THE LENGTH OF THE VALVE BODY AND DEFINING AT LEAST ONE OUTWARDLY DIVERGING PASSAGE WHICH COMMUNICATES WITH THE FUEL PASSAGE THROUGH AN OPENING HAVING A GREATER AREA THAN THE AREA DEFINED BY THE ANNULAR VALVE SEAT. 